1. Field of the Invention
The present invention relates to electronically controlled fuel injection systems for internal combustion engines which are designed so that the amount of fuel injected is controlled by the duration of fuel injection, and more particularly the invention relates to such fuel injection system wherein the time of fuel injection ending is improved to be substantially synchronized with a predetermined rotational angle of the engine.
2. Description of the Prior Art
In the past, there have been electronically controlled fuel injection systems in which the amount of fuel supplied to an internal combustion engine is controlled in accordance with the duration of fuel injection by the opening of fuel injectors, and in a system of this type the beginning of fuel injection is synchronized with a predetermined rotational angle of the engine crankshaft. Thus, if, for example, the beginning of fuel injection is synchronized with the beginning of the suction stroke in the case of a four-cycle internal combustion engine, the injection time per stroke will be reduced at high engine rotational speeds with the resulting danger of causing the fuel injection to extend over part of the following compression stroke. Thus, particularly in the case of an engine in which fuel is fed directly into the engine, there is a disadvantage that the high cylinder pressure causes insufficient injection of fuel. Also, in the case of a two-cycle internal combustion engine, there is a disadvantage that since the suction stroke and the scavenging stroke overlap each other, the injection of the fuel is continued even during the scavenging process, thus causing the emission of unburned gases.